Internet Protocol (IP) multicast enables modern data networks to save bandwidth and processing capacity by reducing the number of copies of data packets transmitted from a source to a destination. In a traditional unicast model, source devices transmit content (e.g., a video file, etc.) directly to a destination device by referencing an IP address associated with the destination device. Therefore, even if multiple destination devices are requesting the same content at the same time, multiple copies of the content are transmitted simultaneously. While this model is effective for on-demand content-related activity, such as web browsing, it is inefficient for some types of media distributions, such as streaming video for IP television, distance learning, etc.
Multicast operates in a manner more similar to a traditional broadcast model. Destination devices wishing to receive content from a particular source join a multicast group designated by a particular address. The content is delivered to all destinations associated with the address. Because they share a common address, known as the multicast group address, only a single copy of the content needs to be transmitted across any single hop in a network, such as between routers, etc.
Unfortunately, implementing IP multicast (IP being a layer 3 protocol) on a layer 2 network, such as the ATM network which forms the basis of many broadband passive optical networks (BPONs), typically requires significant overhead, thereby reducing its effectiveness.